My turn... Suspension "clunk"

[fitzski]

I've developed a pretty dramatic "clunk"-ing noise over the last three days, and I wonder what opinions folks may have.

A couple of caveats:
1) I just replaced the suspension (myself) - Koni FSD w/Eibach springs... all went well, I didn't have to lower the sub-frame, and I've been running it for ~10 days with no clunk

2) The clunk does seem to have started after hitting a speed bump, or rather, the side of a speed hump that does not quite span the entire width of road... I was forced to the right side of the road by an oncoming trailer as I approached a speed hump... the left front went over the hump, while the right front did not have to, and I definitely hit *something* on the under carriage. I first noticed the clunk on the way home that evening, and it seems to have gotten marginally worse since.

I don't get the clunk going over bumps, unless the car is being torqued (twisted); it's more common while turning, right or left, especially if getting on or off the accelerator or brake. I can take on- and off-ramps with no noise, however.

It's a definite CLUNK... a borderline thud... and you can feel it in the car and it's not feint. Only happens once, not repeatedly - motor mount? Doesn't sound to me like swaybar bushings.

I pulled the front wheels off last night to inspect bushings and tighten suspension bolts, but didn't find anything out of the ordinary. It's not readily apparent where I hit the under carriage either... the OEM (plastic) skidplate is intact, and I didn't notice any impact marks on the lower control arm or sub-frame.

I'll put it on the ramps tonight and pull the skidplate off... but what should I look for?

 

[Powder Hound]

Is the clunk coming from the front or rear? If the rear, check to see if the beam axle was dinged.

On the front, anything that can move with the suspension will be suspect, concentrating of course on the left side where the edge of the speep bump would have hit something.

It might be a subtle as a nick hitting something else - lower control arm, roll bar mount, edge of a bushing, bent bolt.

Look for fresh scrapes/scratches in the paint to show you where to look for damage. Good luck. If you can, pictures would be great!

 

[fitzski]

Thanks... hopefully there will be something apparent once I get the skidplate off. Definitely feels like it's coming from the front, more likely on the right side (which is where contact was made with the speed bump), though kinda difficult to pinpoint - sorta feels in the middle (which would point to swaybar bushings?).

I guess one question I have is: can I "see" a worn or bad bushing? Is it going to be apparent that "oh yeah, look here... that's the problem", or do I just start replacing them on spec (swaybar... control arms... etc)?

I may try disconnecting the swaybar and going for a short drive to rule it out (or in, as the case may be!).

 

[Gretta_the_Jetta]

I'd focus on the sway bar bushings and linkages. I had a similar incident on a previous car - went over a bump...heard a thud and something fell off the car. As I drove down the road, whenever I would hit a bump I would hear a thud as well...sometimes several depending on the bump I hit. When I got home I didn't notice anything right away until after I removed the wheel. To my surprise the sway bar bushing top had popped off and the drivers side sway bar was not connected to anything. the thud I heard was the swaybar hitting the broken mount when going over a bump. It turns out the bolt that held the bushings together with the swaybar had rusted out and litterally sheared off midpoint. A new set of bushings, a hacksaw to cut the other side off (too rusted to unbolt) and 45 minutes was all it took.

 

[je]

Mine does that because the bearings atop the struts are cracked, again.

You'd think that after doing that a few times re-doing the suspension I'd learn not to tighten it (or re-tighten it) so much, but I don't learn.

It's worst when that wheel goes down a bump, like a driveway or turning in the wheel's direction (it's the left wheel, so a hard left turn that extends the strut).

 

[greengeeker]

fitzski, a swaybar bushing should have a line-to-line contact with the swaybar when sitting on level ground. If you see a gap it's time to replace.

 

[fitzski]

Mine does that because the bearings atop the struts are cracked, again.

You'd think that after doing that a few times re-doing the suspension I'd learn not to tighten it (or re-tighten it) so much, but I don't learn.

It's worst when that wheel goes down a bump, like a driveway or turning in the wheel's direction (it's the left wheel, so a hard left turn that extends the strut).

hmm... that's a possibility... properly torquing the inner strut nut (the one against the bearing) is a bit tricky - I could have easily over-tightened it, and the impact from that bump may have cracked it. I'll test out the swaybar bushings tonight, proceed to drop the skidplate and look for anything else obvious (tranny mount...), and then resort to inspecting the strut bearing if I don't get anywhere.

 

[fitzski]

Disconnected the swaybar end links last night and went for a drive... didn't notice the clunk, despite trying pretty hard. Bushings looked fine to me (i.e. tight around the bar, no noticeable slop in the bar, at least not that l'il old me could induce when lying under the car, grabbing each end and flexing it).

Only oddity was the right front end link... I couldn't get the lower bolt back through the end link bushing into the lower control arm. Close inspection of the end link (I have the newer plastic ones on my '04) looks like that may be where I contacted the speed hump (there is a small abrasion, and one of the plastic "fins" is cracked). I think the bushing in the end link got twisted from the slight impact, which then binds on the bolt (which does not appear bent). To get it back together, I had to disconnect the top bolt and thread the bottom bolt first.

Once reconnected, another test drive yielded no clunk... go figure. I was optimistic that a re&re solved it, so didn't bother pulling off the skidplate to look for anything else.

However, my wife reports hearing the clunk on the morning drive this AM.

For the price, I may as well replace the swaybar bushings, and probably the end link. If I do one end link, should I do both?

Also... can someone confirm 11 ft-lbs for the top and bottom end link bolts? That really ain't much (maybe a 1/4 turn from finger tight!), especially since the Bentley actually says to always replace the top bolt.

 

[roadhard1960]

On my car I have felt a clunk from the brakes when backing out of the garage. Also clunks sometimes on rough roads. I am 93.2% sure it is the rear bushings on the A-arm. They look pretty rough. I have new bushings but no inclination to take things apart yet. Most of our roads are pretty smooth. I would be obsessing if I still lived in Ohio with their bumpy roads.

My manual shows 22 lb ft for the top nut. 33 for the bolt that goes in to the control arm.

 

[fitzski]

Thx... sorry, I meant 33 ft-lbs... not sure where the 11 came from (I was checking a bunch of things in the Bentley last night).

 

[fitzski]

hrm... re: torque figures... always a moving target... 33 ft-lb is what I got from Wingnut's swaybar bushing how-to, and here, from page 40-3 in my Bentley:

item 14 (end link, bottom bolt) 15 N-m (11 ft-lb)
item 15 (end link, top nut) 15 N-m (11 ft-lb), always replace
item 27 (swaybar bushing bracket bolt) 25 N-m (18 ft-lb)

On topic... drove the car tonight, no clunking. I think my wife was mistaken (first time she's driven with the new suspension in, so probably just felt a bit different/harsher than she recalls). I'm confident that properly aligning that lower end link bolt put things right. Some of the threads were a bit mangled, so I chased it with the bolt in and out a few times and it seems OK.

 

[je]

Today I looked at the bearing I thought was cracked.

It was perfectly good, not cracked at all.

Wow, that took 2 hours and 4 spring compressors trying to put the works back together!

Must be something else then. Perhaps I didn't tighten the lower of the two top nuts enough.

 

[fitzski]

Another day... to and from work (~100km)... no clunk. I'm gonna let things alone unless I hear the clunk again.

je... try disconnecting the swaybar and go for a drive. Easy enough to do (you can reach the lower end link bolt with the car on the ground), and lets you isolate a possible source.

With the lower bolt removed from each side, you can rotate the sway bar a bit to swing the end links away from where they might interfere with the lower control arm while driving.